Listening to the flow of light

[Michael Lee]

Although I don't know if it's that good of an ITC entropy / noise source, I think it is pretty cool that we can actually hear the flow of photons from a laser or flashlight.

• Simply make a circuit of 48V (phantom power) -> 10K resistor -> PhotoTransistor (PT) -> Gnd (audio interface output). I use a BPW85A (purchaseable from Mouser for ~$1 each)
• Turn off all the lights
• Take a continuous light source (either a bright flashlight or pen laser) and point it at the PT face. Then slowly turn it away. You should hear a click sound as the voltage goes from high to near zero.
• Then, carefully adjust the light until you're getting lots of clicks. You should hear what sounds like pink or white noise if you get it just right.
• I think this noise is a stream photons hitting the phototransistor and generating a current that is neither saturated or not registering.
• This noise can be "filtered" with denoising, etc. to obtain spirit voice, but as I said at the outset, I don't think it's the most productive medium for spirit voices, likely because it stems from the noisy circuitry of the light source.
• One could imagine fancier light fields with mirrors, more than one light source, absorbent materials, water, smoke, etc.

[Andres Ramos]

On 1/4/2021 at 5:58 AM, Michael Lee said:

Although I don't know if it's that good of an ITC entropy / noise source, I think it is pretty cool that we can actually hear the flow of photons from a laser or flashlight.

• Simply make a circuit of 48V (phantom power) -> 10K resistor -> PhotoTransistor (PT) -> Gnd (audio interface output). I use a BPW85A (purchaseable from Mouser for ~$1 each)
• Turn off all the lights
• Take a continuous light source (either a bright flashlight or pen laser) and point it at the PT face. Then slowly turn it away. You should hear a click sound as the voltage goes from high to near zero.
• Then, carefully adjust the light until you're getting lots of clicks. You should hear what sounds like pink or white noise if you get it just right.
• I think this noise is a stream photons hitting the phototransistor and generating a current that is neither saturated or not registering.
• This noise can be "filtered" with denoising, etc. to obtain spirit voice, but as I said at the outset, I don't think it's the most productive medium for spirit voices, likely because it stems from the noisy circuitry of the light source.
• One could imagine fancier light fields with mirrors, more than one light source, absorbent materials, water, smoke, etc.

By "turning away the light source from the PT" that means you adjust the light source in a way that only a part from its rim is is shedding light on the PT?

[Michael Lee]

Yes. I assume it's the point where the current is in between saturation and zero.

[L. Garrigue]

And the use of light is always very elegant
Reminds me the photonic quantum computer
https://science.sciencemag.org/content/370/6523/1460